COMBINED CYCLE POWER GENERATION PLANT

CENTRALE ELECTRIQUE A CYCLE COMBINE

English Abstract

In a combined cycle power generation plant in which
a gas turbine high temperature portion is cooled by steam,
pressure loss of the cooling steam is prevented from becoming
larger and the cooling steam is recovered efficiently.
The high temperature portion of gas turbine
stationary blade or moving blade is provided with a plurality
of mutually independent passages which are arranged in
parallel, thereby pressure loss causing portions of the
cooling steam are dispersed corresponding to the number of
positions of the parallel arrangement and aggregate of all
the pressure losses can be reduced.

French Abstract

Dans une centrale électrique à cycle combiné, la partie à température élevée de l'aube d'une turbine à gaz est refroidie au moyen de vapeur. L'invention propose d'empêcher l'aggravation du problème de la perte de pression de la vapeur de refroidissement et de permettre une récupération efficace de la vapeur de refroidissement. La partie où la température est élevée dans l'aube stationnaire ou en mouvement d'une turbine à gaz est pourvue de nombreux passages mutuellement indépendants disposés en parallèle et la perte de pression subie au niveau des passages de vapeur de refroidissement est répartie entre le nombre de passages arrangés en parallèle; il est donc possible de réduire les pertes globales de pression.

Claims

IN THE CLAIMS:

1. A combined cycle power generation plant,
comprising:
a gas turbine having rotary blades;
a steam turbine;
a cooling system to use steam to cool the
rotary blades of the gas turbine, wherein said cooling system
includes a first plurality of cooling passages arranged in
parallel to convey the steam to cool the rotary blades; and
a recovery system to recover the steam after
the rotary blades have been cooled thereby, and then to feed
the recovered steam to the steam turbine.

2. The combined cycle power generation plant
according to claim l, wherein the rotary blades include a
first stage rotary blade and a second stage rotary blade.

3. The combined cycle power generation plant
according to claim 2, and further comprising a first supply
channel in fluid communication with said first plurality of
cooling passages.

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4. The combined cycle power generation plant
according to claim 3, wherein said recovery system includes a
first plurality of recovery passages in fluid communication
with said first plurality of cooling passages, respectively,
and a first recovery channel in fluid communication with said
first plurality of recovery passages.

5. The combined cycle power generation plant
according to claim 4, wherein said gas turbine further
includes a first stage stationary blade and a second stage
stationary blade, wherein said cooling system further includes
a second plurality of cooling passages arranged in parallel to
convey steam to cool the first stage stationary blade and the
second stage stationary blade, and wherein said recovery
system is to also recover this steam after the first stage
stationary blade and the second stage stationary blade have
been cooled thereby and then to also feed this recovered steam
to the steam turbine.

6. The combined cycle power generation plant
according to claim 5, and further comprising a second supply

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channel in fluid communication with said second plurality of
cooling passages.

7. The combined cycle power generation plant
according to claim 6, wherein said recovery system further
includes a second plurality of recovery passages in fluid
communication with said second plurality of cooling passages,
respectively, and a second recovery channel in fluid
communication with said second plurality of recovery passages.

8. The combined cycle power generation plant
according to claim 1, wherein said gas turbine further
includes a first stage stationary blade and a second
stationary blade, wherein said cooling system further includes
a second plurality of cooling passages arranged in parallel to
convey steam to cool the first stage stationary blade and the
second stage stationary blade, and wherein said recovery
system is to also recover this steam after the first stage
stationary blade and the second stage stationary blade have
been cooled thereby and then to also feed this recovered steam
to the steam turbine.

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9. The combined cycle power generation plant
according to claim 8, and further comprising a second supply
channel in fluid communication with said second plurality of
cooling passages, and wherein said recovery system includes a
second plurality of recovery passages in fluid communication
with said second plurality of cooling passages, respectively,
and a second recovery channel in fluid communication with said
second plurality of recovery passages.

10. The combined power generation plant according
to claim l, wherein the rotary blades include a blade set of
one stage, with said blade set being divided into a plurality
of groups, and wherein said plurality of cooling passages are
associated with said plurality of groups, respectively.

11. The combined power generation plant according
to claim 10 wherein said cooling steam passage is sectioned
into plural pieces in the circumferential direction with
respect to same one stage as well as is constructed by
parallel cooling steam passages relative to a first stage
moving blade and a second stage moving blade in which a

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plurality of mutually independent passages are arranged in
parallel.

12. A steam system for a combined cycle power
generation plant including a gas turbine and a steam turbine,
said steam system comprising:
a cooling system operable to use steam to cool
rotary blades of the gas turbine, wherein said cooling system
includes a first plurality of cooling passages arranged in
parallel to convey the steam to cool the rotary blades; and
a recovery system operable to recover the
steam after the rotary blades have been cooled thereby, and
then to feed the recovered steam to the steam turbine.

13. The steam system according to claim 12,
wherein the cooling system is operable to use steam to cool
the rotary blades including a first stage rotary blade and a
second stage rotary blade.

14. The steam system according to claim 13, and
further comprising a first supply channel in fluid
communication with said first plurality of cooling passages.

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15. The steam system according to claim 14, wherein
said recovery system includes a first plurality of recovery
passages in fluid communication with said first plurality of
cooling passages, respectively, and a first recovery channel
in fluid communication with said first plurality of recovery
passages.

16. The steam system according to claim 15, wherein
said cooling system is also operable to cool a first stage
stationary blade and a second stage stationary blade of the
gas turbine, wherein said cooling system further includes a
second plurality of cooling passages arranged in parallel to
convey steam to cool the first stage stationary blade and the
second stage stationary blade, and wherein said recovery
system is also operable to recover this steam after the first
stage stationary blade and the second stage stationary blade
have been cooled thereby and then to feed this recovered steam
to the steam turbine.

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17. The steam system according to claim 16, and
further comprising a second supply channel in fluid
communication with said second plurality of cooling passages.

18. The steam system according to claim 17,
wherein said recovery system further includes a second
plurality of recovery passages in fluid communication with
said second plurality of cooling passages, respectively, and a
second recovery channel in fluid communication with said
second plurality of recovery passages.

19. The steam system according to claim 12,
wherein said cooling system is also operable to cool a first
stage stationary blade and a second stage stationary blade of
the gas turbine, wherein said cooling system further includes
a second plurality of cooling passages arranged in parallel to
convey steam to cool the first stage stationary blade and the
second stage stationary blade, and wherein said recovery
system is also operable to recover this steam after the first
stage stationary blade and the second stage stationary blade
have been cooled thereby and then to feed this recovered steam
to the steam turbine.

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20. The steam system according to claim 19, and
further comprising a second supply channel in fluid
communication with said second plurality of cooling passages,
and wherein said recovery system includes a second plurality
of recovery passages in fluid communication with said second
plurality of cooling passages, respectively, and a second
recovery channel in fluid communication with said second
plurality of recovery passages.

21. The steam system according to claim 12,
wherein said cooling system is operable to use steam to cool
the rotary blades including a blade set of one stage, wherein
the blade set is divided into a plurality of groups, and
wherein said plurality of cooling passages are associated with
said plurality of groups, respectively.

22. The steam system according to claim 21,
wherein said cooling steam passage is sectioned into plural
pieces in the circumferential direction with respect to same
one stage as well as is constructed by parallel cooling steam
passages relative to a first stage moving blade and a second

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stage moving blade in which a plurality of mutually
independent passages are arranged in parallel.

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Description

_ CA 02242071 1998-06-30
COMBINED CYCLE POWER GENERATION PLANT
BACKGROUND OF THE INVENTION:
Field of the Invention:
The present invention relates to a combined cycle
power generation plant constructed by combining a gas turbine
plant and a steam turbine plant.
Description of the Prior Art:
A combined cycle power generation plant is a power
generation system constructed by combining a gas turbine plant
and a steam turbine plant and a high temperature range of
thermal energy is taken charge of by a gas turbine and a low
temperature range of same by a steam turbine, thus the thermal
energy is recovered and made use of effectively and this power
generation system is now going to be used widely.
In said combined cycle power generation plant,
research and development thereof has been done with emphasis
being put on how far the high temperature range of gas turbine
can be heightened as one point for enhancing the efficiency.
On the other hand, there must be provided a cooling
system for securing heat resistance of gas turbine structure
for forming the high temperature range and air has been used
as cooling medium in this cooling system.
However, so far as air is used as cooling medium, even
if the high temperature range is attained, there are problems
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_ CA 02242071 1998-06-30
which prevent thermal efficiency from being enhanced further,
said problems being such that there is caused a power loss at
own air compressor for elevating pressure of air which has been
used for cooling to a necessary level and there occurs a
lowering of mean gas temperature of a high temperature gas
flowing in high temperature gas passages in the turbine when
the high temperature gas is mixed with the air which has been
used for cooling of the turbine, which results in lowering of
energy contained therein.
In order to dissolve said problems and to enhance
efficiency further, cooling system using steam in place of air
as the cooling medium has been disclosed.
One example thereof is an invention of the Japanese
laid-open patent No. Hei 05(1993)-163960, which discloses an
idea to employ steam as the cooling medium of gas turbine but
there are remained various problems therein which have to be
devised and solved in detail.
For example, said invention discloses substantially
only a basic idea that a cooling steam is supplied into a high
temperature portion to be cooled of gas turbine from a certain
steam source to flow through portions to be cooled and then to
be led into a recovery portion after it has done a predetermined
work and there is mentioned therein nothing of particular
consideration on problems of pressure loss of the cooling steam
and the like in that process of work.
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That is, as to the art of steam cooling, it is still
a stage of try and error wherein no satisfactory prior art is
seen yet as to detailed pursuit, device, consideration,
countermeasure, etc. of the problems as mentioned above.
The prior art remains still in a basic idea, as
mentioned above, wherein cooling steam passages are formed in
series so as to communicate one to another along an entire
portion to be cooled in a stationary system and a rotating
system, respectively.
That is, the high temperature portion to be cooled
in the stationary system is constructed such that the cooling
steam flows in series through a first stage stationary blade
and then a second stage stationary blade communicating thereto
to be heated through a predetermined cooling and then to flow
to a recovery portion.
In such a construction, there is caused a large
pressure loss at the high temperature portion to be cooled of
the gas turbine so that there occur various restrictions on the
upstream side and the downstream side of the high temperature
portion to be cooled which make freedom smaller not only of
designing and manufacturing but also of operation and bring on
lowering of plant efficiency. That is, if pressure of the
cooling steam is lowered when it is to be recovered after
cooling of the high temperature portion to be cooled, output
of steam turbine is reduced by that degree of pressure lowering,
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CA 02242071 2000-11-08
which brings on lowering of plant efficiency.
On the other hand, if a predetermined pressure is to
be obtained continuously at the steam turbine with said
pressure loss being considered in advance, it requires a
control valve of which capacity is larger than needed. This
not only means increase of cost in designing and manufacturing
but also employment of control valve of such a large capacity
will be impractical.
SUMMARY OF THE INVENTION:
In view of the mentioned problems in the prior art,
it is an object of the present invention to provide a combined
cycle power generation plant in which pressure loss is
prevented from becoming larger at a high temperature portion
to be cooled of gas turbine and a cooling steam is recovered
efficiently.
In order to attain said object, the present invention
provides a combined cycle power generation plant,
comprising a gas turbine having rotary blades; a steam
turbine; a cooling system to use steam to cool the rotary
blades of the gas turbine, wherein said coolina system
includes a first plurality of cooling passages arranged in
parallel to convey the steam to cool the rotary blades;
and a recovery system to recover the steam after the
rotary blades have been cooled thereby, and then to feed
the recovered steam to the steam turbine.
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CA 02242071 2000-11-08
There is provided at the gas turbine
independent parallel cooling steam passages. Because the
cooling steam passages art: arranged in parallel,
locations at which pressure loss of the cooling steam can
occur are dispersed, whereby an aggregate of all the
pressure losses can be reduced.
In one embodiment, the present invention
provides a combined cycle power generation plant as
mentioned above, wherein the parallel cooling steam
passages consist of a cooling steam passage of a first
stage stationary blade, and a cooling steam passage of a
second stage stationary blade. Specifically, the
stationary blades are provided with mutually independent
cooling steam passages which are between the first stage
stationary blade and the second stage stationary blade,
whereby the pressure loss at the cooling steam passages
is dispersed, and hence an aggregate of all the pressure
losses can be reduced.
Also in this embodiment, the present invention
provides a combined cycle power generation plant as
mentioned above, wherein the parallel cooling steam
passages consist of a cooling steam passage of a first
stage moving blade, and a cooling steam passage of a
second stage moving blade. Specifically, the moving blades
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CA 02242071 2000-11-08
are provided with mutually independent cooling steam
passages which are between the first stage moving blade
and the second stage moving blade, whereby the pressure
loss at the cooling steam passages is dispersed, and hence
an aggregate of all the pressure losses can be reduced.
In a second embodiment, the present invention
provides a combined cycle power generation plant as
mentioned above, wherein the parallel cooling steam
passages consist of a plurality of mutually independent
and parallel cooling steam passage systems, with each
system comprising a plurality of stationary blades or
moving blades sectioned with respect to one another in the
same stage. Thus, the pressure loss at the cooling steam
passages is dispersed, and hence an aggregate of all the
pressure losses can be reduced.
BRIEF DESCRIPTION OF THE DRAWINGS:
Fig. 1 is an axial cross sectional view showing very
schematically a main part of gas turbine cooled portion of a
first embodiment according to the present invention.
Fig. 2 is a radial cross sectional view showing very
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_ CA 02242071 1998-06-30
schematically a main part of gas turbine cooled portion of a
second embodiment according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS:
A first embodiment according to the present invention
will be described with reference to Fig. 1. Fig. 1 is a view
showing a main part of the first embodiment very schematically
for simplicity of description.
Numeral 1 designates a first stage stationary blade,
numeral 2 designates a second stage stationary blade, numeral
3 des ignate a f first stage moving blade and numeral 4 des ignates
a second stage moving blade. Numeral 5 designates a cooling
steam supply channel, which branches midway to communicate to
a cooling steam passage 5a of the first stage stationary blade
1 and a cooling steam passage 5b of the second stage stationary
blade 2.
The cooling steam passage 5a communicates to a steam
recovery passage 6a of the first stage stationary blade 1 via
a portion to be cooled of the first stage stationary blade 1
and the cooling steam passage 5b communicates to a steam
recovery passage 6b of the second stage stationary blade 2 via
a portion to be cooled of the second stage stationary blade 2
and both the steam recovery passages 6a and 6b join together
downstream thereof to communicate to a steam recovery passage
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- CA 02242071 1998-06-30
That is, the cooling steam passage 5a at a position
of the first stage stationary blade 1 and the cooling steam
passage 5b at a position of the second stage stationary blade
2 form mutually independent and parallel passages and the steam
recovery passages 6a and 6b communicating thereto form likewise
mutually independent and parallel passages.
On the other hand, if seen on the moving blade side,
symmetrically to the stationary blade side numeral 7 designates
a cooling steam supply channel, which branches midway to
communicate to a cooling steam passage 7a of the first stage
moving blade 3 and a cooling steam passage 7b of the second stage
moving blade 4.
And the cooling steam passage 7a communicates to a
steam recovery passage 8a of the first stage moving blade 3 via
a portion to be cooled of the first stage moving blade 3 and
the cooling steam passage 7b communicates to a steam recovery
passage 8b of the second stage moving blade 4 via a portion to
be cooled of the second stage moving blade 4 and both the steam
recovery passages 8a and 8b join together downstream thereof
to communicate to a steam recovery passage 8.
That is, like the stationary blade side, the cooling
steam passage 7a at a position of the first stage moving blade
3 and the cooling steam passage 7b at a position of the second
stage moving blade 4 form mutually independent and parallel
passages and the steam recovery passages 8a and 8b
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- CA 02242071 1998-06-30
communicating thereto form likewise mutually independent and
parallel passages.
In the present embodiment constructed as mentioned
above, if seen on the stationary blade side first, the cooling
steam supplied from an outside cooling steam supply source
which is not shown is fed from the cooling steam supply channel
5 to branch to the cooling steam passages 5a, 5b so as to be
led into the first stage stationary blade 1 and the second stage
stationary blade 2. Then, the cooling steam itself is heated
through cooling the high temperature portions to be cooled of
the first stage stationary blade 1 and the second stage
stationary blade 2 and joins into the steam recovery passage
6 via the mutually independent and parallel recovery-passages
6a, 6b to be heat-recovered at a steam turbine and the like which
are not shown.
In this case, the cooling steam flowing in the cooling
steam passage 5a has nothing to do with a pressure loss due to
the cooling steam passage 5b and the cooling steam flowing in
the cooling steam passage 5b has nothing to do with a pressure
loss due to the cooling steam passage 5a, hence the pressure
loss as a whole is reduced greatly.
On the other hand, if seen on the moving blade side,
the situation is quite same as the stationary blade side and
it will be easily understood without repeated explanation that
the cooling steam flows with a reduced pressure loss and is
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- CA 02242071 1998-06-30
heat-recovered at a steam turbine and the like which are not
shown via the steam recovery passage 8.
Next, a second embodiment according to the present
invention will be described with reference to Fig. 2. Fig. 2
is a view showing a main part of the second embodiment very
schematically also for simplicity of description.
Numeral 10 designates a blade set is same one stage,
shown imaginably, comprising a multitude of stationary blades
or moving blades along the entire circumference. The blade set
10 here is sectioned into six groups, each forming a group of
independent cooling steam passage system, so that said groups
of system are arranged mutually in parallel along the
circumferential direction.
That is, a cooling steam passage 11 of a first blade
group comprises a cooling steam supply channel lla and a steam
recovery passage llb, and a cooling steam passage 12 of a second
blade group comprises a cooling steam supply channel 12a and
a steam recovery passage 12b, and likewise thereafter cooling
steam passages 13, 14, 15 and 16 of 3rd, 4th, 5th and 6th blade
groups comprise cooling steam supply channels 13a, 14a, 15a and
16a and steam recovery passages 13b, 14b, 15b and 16b,
respectively, so that these six groups are arranged mutually
in parallel.
In the present embodiment also, the cooling steam
passages are sectioned in parallel along the circumferential
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- CA 02242071 1998-06-30
direction as mentioned above, hence the pressure loss is
dispersed and suppressed, like the first embodiment, and heat
recovery is carried out likewise at a steam turbine and the like
which are not shown.
The present invention has been described with respect
to the embodiments shown in the figures, but the present
invention is not limited thereto but, needless to mention; may
be added with various modifications in the concrete structure
within the scope of claims as hereinbelow set forth.
According to the present invention, following effect
can be obtained. That is, the cooling steam flows separately
in the mutually independent and parallel passages, hence
comparing with such case that all the cooling steam-flows in
series through common pressure loss causing portions so that
the pressure loss is accumulated to become larger, there occurs
no such case in the present invention and an effective apparatus
having a suppressed pressure loss and thus having no
unnecessary troubles in the downstream equipment can be
obtained.
Also, by employing such a structure that the first
and second stage stationary blades are cooled in parallel with
heat recovery being carried out as well, an effective apparatus
having a suppressed pressure loss can be obtained.
Also, by employing such a structure that the first
and second stage moving blades are cooled in parallel with heat
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_ CA 02242071 1998-06-30
recovery being carried out as well, an effective apparatus
having a suppressed pressure loss can be obtained.
Further, by employing such a structure that the blade
groups in same one stage of stationary blades or moving blades
are cooled in parallel with heat recovery being carried out as
well, an effective apparatus having a suppressed pressure loss
can be obtained.
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Representative Drawing